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Full text of "The Morphology And Evolution Of The Apes And Man"

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>              MOBPHOLOGT AND BYOLTJTION
Papillary   ridges   are   also   present   on   the   gripping surfaces of prehensile tails.
The epidermis is thickened to form the ischial callosities in the Gibbons and Monkeys.
The mammary glands vary in position. In the Lorises and Tarsiits there are both inguinal and pectoral mammae ; in the Aye-Aye (CJiiromys) they are restricted to the groins; in Hapalemur they occur on the shoulders; and in all other Primates there ate two pectoral mammae, Phylogenetically the mammary glands are modified sebaceous glands. In some Primates there are also specially modified sebaceous glands which have an erotic function.
The digits of the hands and feet are usually five in number, but the thumb is absent in the Spider Monkeys (Atdesi, and the index of the hand is a small stump in the Potto \Perodicticus). The relative lengths of the digits vary considerably.
The digits have nails or claws, but it is sometimes difficult to decide whether a particular structure is a nail or a claw. In the true Lemurs the inde:g has a claw, but the other digits have nails; in Tarsius there are claws on the second and third digits of the foot; in Chiromt/B there are claws on all digits. Of the New World Monkeys the Marmosets have claws on all digits except the hallux : but the Cebidse possess highly-arched claw-like structures. All Old World Primates have flat nails on all digits, but they are curved in some Gribbons, The digits also exhibit a variable amount of nnion by webs (syndactyly).
The functions of the tail are numerous. In Tarsius it is pressed against the tree trunks and acts as a